Wireless communication system, wireless communication apparatus, wireless communication method, and computer program

ABSTRACT

A wireless communication network that forms an ad-hoc network without the arrangement of a controlling station sets a period that a communication apparatus can utilize with priority and performs isochronous communication in the period as required. When isochronous communication has not been performed or after isochronous communication has finished in the priority utilization period, other communication apparatuses perform arbitrary communication. When another communication is performed in a communication apparatus&#39;s own priority utilization period, the start of isochronous communication is temporarily delayed. In an ad-hoc communication environment, data having a real-time characteristic, such as AV content, can be efficiently transmitted through the isochronous communication.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.14/882,719, filed Oct. 14, 2015, which is a continuation of U.S.application Ser. No. 14/297,312, filed Jun. 5, 2014 (U.S. Pat. No.9,191,965), which is a continuation of U.S. application Ser. No.13/299,775, filed Nov. 18, 2011 (U.S. Pat. No. 8,787,339), which is acontinuation of U.S. application Ser. No. 12/150,492, filed Apr. 29,2008 (U.S. Pat. No. 8,085,744) which is a divisional of U.S. applicationSer. No. 10/510,011, filed Sep. 29, 2004 (U.S. Pat. No. 7,630,334),which is a national stage application of International Application No.PCT/JP04/06101, filed Apr. 27, 2004, which claims priority from JapaneseApplication No. 2003-129546, filed May 7, 2003, the disclosures of whichare hereby incorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to wireless communication systems,wireless communication apparatuses, wireless communication methods, andcomputer programs which mutually perform communication between aplurality of wireless stations in a wireless LAN (Local Area Network) orthe like. In particular, the present invention relates to a wirelesscommunication system, a wireless communication apparatus, a wirelesscommunication method, and a computer program which efficiently transmitisochronous data, such as AV content.

More specifically, the present invention relates to a wirelesscommunication system, a wireless communication apparatus, a wirelesscommunication method, and a computer program which efficiently transmitisochronous data in an ad-hoc (ad-hoc) communication environment inwhich individual communication stations forms a network in an autonomousdistributed manner without the relationship of a controlling station anda controlled station. In particular, the present invention relates to awireless communication system, a wireless communication apparatus, awireless communication method, and a computer program which perform datatransmission with a guaranteed bandwidth in an ad-hoc communicationenvironment.

2. Background Art

As a system for freeing users from LAN wiring of a wired scheme,wireless LANs are gaining attention. Since wireless LANs can omit amajority of wire cables in work spaces such as offices, communicationterminals, such as personal computers (PCs), can be moved with relativeease.

In recent years, in conjunction with an increased speed and reduced costof wireless LAN systems, the demand thereon has increased considerably.In particular, recently, in order to construct a small-scale wirelessnetwork with multiple pieces of electronic equipment available aroundpeople to perform information communication, the incorporation of apersonal area network (PAN) is under consideration. For example,frequency bands, such as a 2.5 GHz band, a 5 GHz band, and so on, thatdo require a license of a regulatory agency, are utilized to definedifferent wireless communication systems.

A method that is typically used to configure a local area network usinga wireless technology is that one apparatus that serves as a controllingstation, called an “access point”, is provided in an area to form anetwork under the centralized control of the controlling station. Inthis case, the access point provides synchronization betweencommunication apparatuses in the wireless network. Access control basedon band reservation is performed. That is, a communication apparatusthat attempts to perform isochronous communication first makes areservation with the access point for a band required for theinformation transmission and utilizes a transmission path so that theinformation transmission does not collide with information transmissionof another communication apparatus.

However, when asynchronous communication is performed between atransmitting-side communication apparatus and a receiving-sidecommunication apparatus, wireless communication that goes through anaccess point is always required. Thus, there is a problem in that theutilization efficiency of a transmission path is reduced by half.

In contrast, “ad-hoc (ad-hoc) communication”, in which terminals performwireless communication with each other directly, has been proposed. Inparticular, in a small-scale wireless network constituted by arelatively small number of clients located in the vicinity, ad-hoccommunication that allows arbitrarily terminals to perform wirelesscommunication with each other without use of a particular access pointis considered to be appropriate.

For example, a mode that operates on a peer-to-peer (peer to peer) basisin an autonomous distributed manner without the provision of acontrolling station has been prepared for a wireless LAN system based onIEEE 802.11.

On the other hand, in order to transfer isochronous and time-sequencedata, such as AV content for which data needs to be transmittedperiodically at regular intervals, a bandwidth must be guaranteed.

For example, IEEE 802.11 TG-e is promoting a study for a communicationmethod based on the premise of bandwidth guarantee using a wireless LANsystem.

However, when an attempt is made to guarantee a bandwidth in aconventional wireless LAN system, a typically used approach is that aspecific controlling station is defined so as to centrally controlcommunication resources and to specify time that is activated in alimited manner in a certain group. The right of transmission iscentrally generated at a communication apparatus that serves as atransmitting end of information and a wireless communication apparatusthat serves as a receiving end is dependent on and is controlled by thetransmitting-end communication apparatus.

This case is based on a premise that a communication apparatus thatserves as the specific controlling station is defined, and is notapplicable to a system in which the controlling-station apparatus is notprovided. In particular, when bandwidth-reservation-based communicationis implemented by forming an ad-hoc network without the relationship ofa controlling station and a controlled station, it is difficult todetermine to which range of influence should be considered. Further,since the right of transmission is centrally generated at acommunication apparatus that serves as a transmitting end ofinformation, a notification cannot be issued to indicate that a wirelesscommunication apparatus that serves as a receiving end is in use forreceiving a signal at a predetermined timing.

Also, isochronous communication is performed to transmit isochronousdata, i.e., time-sequential data. In this case, a predeterminedcommunication band (or time) for isochronous communication is reservedin advance and specific communication apparatuses exclusively performcommunication with each other in the communication band (or time).

For example, as a technology that is currently being standardized for awireless personal area network (WPAN) based on IEEE 802.15.3, a schemeis considered in which a predetermined communication band is reserved asa guaranteed time slot (GTS) so that isochronous communication isperformed in the band.

However, in the conventional wireless LAN system, when an attempt ismade to perform bandwidth-guaranteed communication such as isochronouscommunication, there is a need for a scheme for sharing the amount ofits guaranteed bandwidth with another communication apparatus. Thus, acommunication apparatus that serves as a particular controlling stationneeds to be defined so as to centrally manage the amount ofcommunication. In other words, such communication with a guaranteedbandwidth is not directly applicable to a wireless communication systemthat does not have the relationship of a controlling station and acontrolled station.

Further, communication between other apparatuses needs to be preventedfrom communicating with each other at time when isochronouscommunication is performed. Thus, in this respect, the controllingstation also needs to centrally identify the communication apparatusesthat use the time. That is, it is extremely difficult to realizeband-reservation-based communication, such as isochronous communication,by forming an ad-hoc network.

SUMMARY OF THE INVENTION

The present invention has been made in view of the foregoing problems,and a first aspect of the present invention provides a wirelesscommunication system that forms a network in an autonomous distributedmanner without the relationship of a controlling station and acontrolled station. The wireless communication system is characterizedin that a transmitting-side or receiving-side communication apparatusthat attempts to perform communication with a guaranteed bandwidthissues, to within own communication range, a notification indicating asetting of a bandwidth guaranteed period and another communicationapparatus that receives the notification does not perform acommunication operation in the bandwidth guaranteed period, therebyavoiding signal collision and interference in the communication rangeand guaranteeing a bandwidth.

The “system” herein refers to a logically assembled unit of a pluralityof apparatuses (or functional modules that realize specific functions)and individual apparatuses or functional modules may or may not beprovided in a single housing.

In this case, the transmitting-side or receiving-side communicationapparatus may describe information regarding the bandwidth guaranteedperiod in beacon information transmitted for each predetermined frameperiod. Informing of timing utilized for a bandwidth-guaranteedcommunication by using a beacon signal allows any number of neighboringwireless communication apparatuses to be notified in advance that abandwidth-guaranteed communication is to be performed.

Further, the receiving-side communication apparatus may create timingutilized for a bandwidth-guaranteed communication, in a pseudo manner,to have the same state as timing of transmitting own beacon and maynotify of the timing utilized for the bandwidth-guaranteedcommunication. In such a case, a wireless communication apparatus thatexists in a region to be a hidden terminal viewed from thetransmitting-side communication apparatus can also be notified that aband-reservation communication is performed.

The transmitting-side or receiving-side communication apparatus may seta reservation period in its own frame period so as to perform anisochronous communication with a guaranteed bandwidth by exclusivelyutilizing the reservation period.

When each wireless communication apparatus notifies of timing the selfcan utilize for a band-reservation communication, it is possible toachieve a band-reservation communication without the relationship of acontrolling station and a controlled station. Each communicationapparatus can exclusively use a reserved slot. Another communicationapparatus cannot use the reserved slot without undergoing a specialprocedure, such as clearing the reservation.

Each communication apparatus restrains a communication operation in areservation period set by another communication apparatus. As a result,communication collision and interference are avoided. That is, eachcommunication apparatus collects beacon information from neighboringcommunication apparatuses; obtains information regarding bandwidthguaranteed periods; and does not set, as the own bandwidth guaranteedperiod, a period that is set as the bandwidth guaranteed periods by theneighboring communication apparatuses. Also, the transmitting-side orreceiving-side communication apparatus collects beacon information fromneighboring communication apparatuses; obtains information regardingbandwidth guaranteed periods; and sets, as the own bandwidth guaranteedperiod, a period that is not set as the bandwidth guaranteed periods bythe neighboring communication apparatuses. This can achieve isochronouscommunication based on band reservation in an ad-hoc network and canensure a band during transmission of isochronous data, such as AVcontent.

Further, a second aspect of the present invention provides a wirelesscommunication system that forms a network in an autonomous distributedmanner without the relationship of a controlling station and acontrolled station. The wireless communication apparatus ischaracterized in that a transmitting-side or receiving-sidecommunication apparatus sets a period utilizable with priority in ownframe period and performs communication with a guaranteed bandwidth byutilizing the priority utilization period with priority, to therebyperform an isochronous communication with a guaranteed bandwidth byutilizing the priority utilization period with priority while avoidingsignal collision and interference in the communication range.

The above-noted reservation period is an exclusively-occupied timeperiod and thus a transmission path is exclusively used by particularcommunication apparatuses. In a method for performing communication byexclusively using a transmission path over a predetermined communicationband (time), when an isochronous communication that does not fill theonce-set predetermined communication band (time) is performed, theinsufficient portion cannot be used for communication between othercommunication apparatuses and thus the throughput decreases. On theother hand, in an access control method based on CSMA (or PSMA)/CA, eachcommunication apparatus performs a collision avoidance operation thatstarts transmission after detecting that no transmission is performedfrom another communication, and thus communication is started unless acarrier signal is detected. This makes it impossible to guarantee that atransmission path is exclusively occupied and utilized for a specificcommunication.

Accordingly, in the second aspect of the present invention, eachwireless communication apparatus sets a period (timing) that the selfcan utilize with priority and performs isochronous communication in thepriority utilization period with priority, as required.

In this case, before the priority utilization period ends, when anisochronous communication with a guaranteed bandwidth betweentransmitting-side communication apparatus and the receiving-sidecommunication apparatus has finished, i.e., when the priorityutilization time has finished, arbitrary communication between othercommunication apparatuses may be performed.

The priority utilization period herein refers to a period that acommunication can utilize with priority and is different from areservation period in which a communication apparatus that has made areservation exclusively uses a transmission path. In the priorityutilization period, priority utilization of a bandwidth is guaranteed,but utilization by another communication apparatus is not completelyexcluded. Thus, another apparatus can also utilize the band within arange in which the priority utilization is guaranteed. Therefore, whilea communication apparatus sets a period that it can utilize withpriority to perform an isochronous communication, arbitrarilycommunication between other communication apparatuses is permitted whenthat isochronous communication has not been performed or has beenfinished. As a result, when an isochronous communication that does notfill a priority utilization period is performed, the insufficientportion can be used for communication between other communicationapparatuses, thereby improving the throughput.

In a case in which another communication is performed at a point of timewhen a priority utilization period set by the self arrives, thetransmitting-side communication apparatus may temporarily delay thestart of an isochronous communication and may perform transmission basedon a priority utilization after the end of the another communication.

Starting a predetermined isochronous communication after the end ofanother communication can achieve an isochronous communication thatcoexists with another communication. In such a case, while the start ofa priority utilization period is temporarily delayed, it can be expectedthat the throughput is improved in terms of the entire system and thetemporary delay is recovered. This is because the priority utilizationstate is cleared, i.e., a band is released, when an isochronouscommunication that does not fill the priority utilization period isperformed.

A third aspect of the present invention provides a computer program thatis described in a computer-readable format so that processing forperforming a wireless communication operation in an autonomousdistributed manner without the relationship of a controlling station anda controlled station is executed on a computer system.

The computer program is characterized by including abandwidth-guaranteed-period setting step of notifying, within owncommunication range, of the setting of a bandwidth guaranteed period inwhich a bandwidth is guaranteed; and a communication controlling step ofexecuting a bandwidth-guaranteed communication in response to thearrival of the own bandwidth guaranteed period.

A fourth aspect of the present invention provides a computer programthat is described in a computer-readable format so that processing forperforming a wireless communication operation in an autonomousdistributed manner without the relationship of a controlling station anda controlled station is executed on a computer system.

The computer program is characterized by including apriority-utilization-period setting step of setting a priorityutilization period for performing communication with a guaranteedbandwidth in own frame period and notifying, within own communicationrange, of the setting of the priority utilization period, and acommunication controlling step of performing communication with aguaranteed bandwidth, with priority, in response to the arrival of theown priority utilization period.

The computer program according to each of the third and fourth aspectsof the invention defines a computer program that is described in acomputer-readable format so that predetermined processing is achieved ona computer system. In other words, installing the computer programaccording to each of the third and fourth aspects of the invention ontoa computer system provides the computer system with a cooperative effectand also causes the computer system to operate as a communicationapparatus. Starting the operation of a plurality of such communicationapparatuses to construct a wireless network can provide the sameadvantages as the wireless communication apparatus according to each ofthe first and second aspects of the present invention.

Further objects, features, and advantages of the present invention willbecome apparent from detailed descriptions based on the followingembodiments of the present invention and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example of arrangement of communication apparatuses thatconstitute a wireless communication apparatus according to oneembodiment of the present invention.

FIG. 2 is a diagram schematically showing the functional configurationof a wireless communication apparatus that operates in the wirelessnetwork environment shown in FIG. 1.

FIG. 3 is a diagram showing an example of the configuration of asuperframe of each wireless communication apparatus in an ad-hoc networkaccording to this embodiment.

FIG. 4 is a diagram showing an example of arrangement of slotsrecognized by each communication apparatus itself.

FIG. 5 is diagram showing a sequence of reservation processing performedby a transmitting side.

FIG. 6 is diagram showing a sequence of reservation processing performedby a receiving side.

FIG. 7 is a diagram showing an example of the configuration of asuperframe when a reservation communication is performed in the ad-hocnetwork according to the embodiment of the present invention.

FIG. 8 is a view showing an example of arrangement of slots recognizedby each communication apparatus itself when performing a reservationcommunication.

FIG. 9 is a diagram showing an example of a sequence of communication ina reservation period.

FIG. 10 is a diagram showing an example of the frame structure of abeacon signal.

FIG. 11 is a diagram showing an example of the frame structure ofreservation request command information.

FIG. 12 is a diagram showing an example of the frame structure ofacknowledgement-notification command information.

FIG. 13 is a diagram showing an example of the frame structure ofreservation notification command information.

FIG. 14 is a diagram showing an example of the frame structure of apseudo beacon signal.

FIG. 15 is a diagram showing an example of the frame structure of an RTScommand.

FIG. 16 is a diagram showing an example of the frame structure of a CTScommand.

FIG. 17 is a diagram showing an example of the frame structure of dataframe.

FIG. 18 is a view showing an example of the frame structure of an ACKframe.

FIG. 19 is a flow chart showing operational procedures of a wirelesscommunication apparatus in the ad-hoc network according to the presentinvention.

FIG. 20 is a diagram showing a state in which each communicationapparatus arranges a priority utilization period in its own superframein the ad-hoc network according to the present invention.

FIG. 21 is a diagram showing a state in which a plurality of pieces ofisochronous information are gathered to provide a priority utilizationperiod.

FIG. 22 is a diagram showing an example of a sequence of communicationin a priority utilization period.

FIG. 23 is a diagram showing another example of a sequence ofcommunication in a priority utilization period.

FIG. 24 is a diagram showing a communication sequence for exchanging apriority utilization period between communication apparatuses thatperform isochronous communication.

FIG. 25 is a diagram showing another example of the communicationsequence for exchanging a priority utilization period betweencommunication apparatuses that perform isochronous communication.

FIG. 26 is a diagram showing an example of the frame structure of beaconinformation.

FIG. 27 is a diagram showing an example of the frame structure of apriority-utilization-period notification command.

FIG. 28 is a flow chart showing processing procedures for a wirelesscommunication apparatus to set and clear a priority utilization periodin the ad-hoc network according to the present invention.

FIG. 29 is a flow chart showing processing procedures for a wirelesscommunication apparatus to perform isochronous communication in thead-hoc network according to the present invention.

DETAILED DESCRIPTION Best Mode for Carrying Out the Invention

Embodiments of the present invention will now be described below indetail with reference to the drawings.

First Embodiment

FIG. 1 shows an example of arrangement of communication apparatuses thatconstitute a wireless communication apparatus according to oneembodiment of the present invention. In this wireless communicationsystem, a specific controlling station is not arranged and individualcommunication apparatuses operate in an autonomous distributed manner toform an ad-hoc network. The figure shows a state in which acommunication apparatus #0 to a communication apparatus #6 aredistributed in the same space.

In the figure, the communication range of each communication apparatusis indicated by a dotted line and is defined as a range in which thecommunication apparatus not only can communicate with anothercommunication apparatus that is located within the range but also asignal transmitted by the self causes interference. That is, thecommunication apparatus #0 is in a range that allows communication withthe communication apparatus #1 and the communication apparatus #4 whichare located in the vicinity. The communication apparatus #1 is also in arange that allows communication with the communication apparatus #0, thecommunication apparatus #2, and the communication apparatus #4 which arelocated in the vicinity. The communication apparatus #2 is also in arange that allows communication with the communication apparatus #1, thecommunication apparatus #3, and the communication apparatus #6 which arelocated in the vicinity. The communication apparatus #3 is in a rangethat allows communication with the communication apparatus #2 located inthe vicinity. The communication apparatus #4 is also in a range thatallows communication with the communication apparatus #0, thecommunication apparatus #1, and the communication apparatus #5 which arelocated in the vicinity. The communication apparatus #5 is in a rangethat allows communication with the communication apparatus #4 located inthe vicinity. The communication apparatus #6 is in a range that allowscommunication with the communication apparatus #2 located in thevicinity.

In this embodiment, each communication apparatus performs access controlutilizing one wireless transmission path in a time-shared manner, whilemutually considering influences with other communication apparatuseslocated in the neighbor.

FIG. 2 schematically shows the functional configuration of a wirelesscommunication apparatus 100 that operates in the wireless networkenvironment shown in FIG. 1. The wireless communication apparatus 100includes an interface 101, a data buffer 102, a central controller 103,a wireless transmitter 104, a timing controller 105, an antenna 106, awireless receiver 107, a control-signal generator 108, a control-signalanalyzer 109, a beacon generator 110, a beacon analyzer 111, and aninformation storage 113.

The interface 101 exchanges various types of information with externalequipment (e.g., a personal computer (not shown)) connected with thewireless communication apparatus 100.

The data buffer 102 is used to temporarily store data transmitted fromthe equipment connected via the interface 101 and data received, beforetransmitting the data via the interface 101.

The central controller 103 centrally performs the management of a seriesof information transmission and reception processing andtransmission-path access control at the wireless communication apparatus100.

In this embodiment, in an ad-hoc network environment in which individualcommunication stations form a network in an autonomous distributedmanner without the relationship of a controlling station and acontrolled station, the wireless communication apparatus 100 performscommunication operation, such as isochronous communication utilizing areservation period or a priority utilization period (described below) ora random-access communication based on the CSMA/CA (Carrier SenseMultiple Access/Collision Avoidance). Each wireless communicationapparatus transmits a beacon at the start of a predetermined frameperiod (hereinafter also referred to a “superframe period”) (the framelengths are uniform, but the frame-start times of communicationapparatuses are not synchronous with each other since they are notcontrolled by a controlling station).

A frame period is constituted by a plurality of slots. The centralcontroller 103 sets a slot that the self utilizes for an isochronouscommunication, stores the content of the setting in the informationstorage 113, and describes the content in a beacon to inform theneighboring wireless communication apparatuses about the content of thesetting.

In order to wirelessly transmit data and a beacon which are temporarilystored in the data buffer 102, the wireless transmitter 104 modulatesthe data and the beacon into, for example, ultra-wide band signals.

The timing controller 105 controls timing of transmitting/receivingultra-wide band signals. For example, the timing controller 105 controlsa reservation period that is already obtained, timing of receiving itsown beacon, timing of receiving a beacon (including a pseudo beacon(described below)) from another communication apparatus, and so on.

The antenna 106 wirelessly transmits signals to another wirelesscommunication apparatus or collects signals transmitted from anotherwireless communication apparatus.

The wireless receiver 107 performs processing for receiving signals ofinformation, a beacon, and so on transmitted from another wirelesscommunication apparatus at predetermined time.

Prior to data transmission, the control-signal generator 108 generatesinformation, such as a reservation request, an acknowledgementnotification, and a reservation notification, as required.

The control-signal analyzer 109 analyzes information of a reservationrequest, an acknowledgement notification, and a reservation notificationtransmitted from a neighboring wireless communication apparatus.

The beacon generator 110 generates a beacon signal that is periodicallyexchanged with wireless communication apparatuses located in thevicinity.

The beacon analyzer 111 analyzes a beacon signal that was able to bereceived from another wireless communication apparatus and analyzes aslot utilized and the presence of a neighboring wireless communicationapparatus.

The information storage 113 stores execution procedure commands, such asa series of access control operations executed by the central controller103 and the address of a neighboring wireless communication apparatusfrom which a beacons has been detected. The information storage 113 alsostores, for example, beacon transmission position (timing) informationof a neighboring wireless communication apparatus that exists in the ownneighbor, parameters (utilization slot information andpriority-utilization-period information) that are described in a beaconand that are associated with a reservation communication of aneighboring wireless communication apparatus.

FIG. 3 shows an example of the configuration of a superframe of eachwireless communication apparatus in the ad-hoc network according to thisembodiment.

In the example shown in this figure, by autonomously determining asuperframe period and periodically transmitting a beacon, eachcommunication apparatus is adapted to cause a neighboring communicationapparatus to recognize the presence of the self. While the frame lengthsare uniform, the frame start time is uniquely set for each communicationapparatus since it is not controlled by a controlling station.

Each wireless communication apparatus transmits its own beacon so thatthe transmission position thereof does not overlap the transmissionpositions of (existing) beacons of neighboring communicationapparatuses, thereby making it possible to construct anautonomous-distributed, ad-hoc network.

In the illustrated example, in the communication apparatus #1, a periodfrom a beacon (B1) to a next beacon (B1′) is defined as a superframeperiod (SF1).

With regard to the communication apparatus #2, when it transmits abeacon (B2), a superframe period (SF2) is defined and a period priorthereto is treated as a superframe period (SF2-1).

With regard to the communication apparatus #3, when it transmits abeacon (B3), a superframe period (SF3) is defined and a period priorthereto is treated as a superframe period (SF3-1).

In this case, the communication apparatus #1 receives a beacon (N2) fromthe communication apparatus #2 located in the vicinity. Thecommunication apparatus #2 receives a beacon (N1) from the communicationapparatus #1 in the vicinity and a beacon (N3) from the communicationapparatus #3. The communication apparatus #3 also receives the beacon(N2) from the communication apparatus #2 in the vicinity.

In the wireless network configuration shown in FIG. 1, the communicationapparatus #1 also receives beacons from the communication apparatuses #0and #4 and the communication apparatus #2 receives a beacon from thecommunication apparatus #6. The details thereof, however, are omittedhere for simplicity of description.

A superframe period is constituted by a plurality of slots (64 lots inthis case) and a slot is a minimum unit of access. FIG. 4 shows anexample of arrangement of slots recognized by each communicationapparatus itself. With reference to its own superframe period (i.e.,with a starting point at the transmission timing of its own beacon), thewireless communication apparatus arranges the slots in terms of arelative position at which a beacon signal is received from aneighboring communication apparatus.

It is shown that the communication apparatus #1 receives a beacon fromthe communication apparatus #2, at the 32nd position, with the ownbeacon transmission position being 0th position.

It is shown that, with the own beacon transmission position being 0thposition, the communication apparatus #2 receives a beacon from thecommunication apparatus #3, at the 18th position, and receives a beaconfrom the communication apparatus #1, at the 32nd position.

It is shown that the communication apparatus #3 receives a beacon fromthe communication apparatus #2, at the 48th position, with the ownbeacon transmission position being 0th position.

In this embodiment, each wireless communication apparatus contains sucha slot arrangement relationship, as a utilization slot informationparameter, in a beacon that is periodically transmitted, and notifiesthe neighboring communication apparatuses about the relationship. Thewireless communication apparatuses then perform processing fortransmitting and receiving information while mutually avoiding slotsutilized by other communication apparatuses. This makes it possible toautonomously form an ad-hoc network while avoiding collision andinterference.

A transmitting-side wireless communication apparatus issues areservation request to a receiving-side wireless communicationapparatus. In response to the reservation request, the receiving-sidewireless communication apparatus returns an acknowledgementnotification. Neighboring communication apparatuses are notified of abeacon in which a reserved utilization slot is described, so that thecommunication apparatuses can use the utilization slot fortransmitting/receiving information to/from each other.

FIG. 5 illustrates a reservation processing sequence. In the illustratedexample, equipment connected with the communication apparatus #1 thatserves as a transmitting end of reservation communication issues areservation instruction and the receiving-end communication apparatus #2responds thereto to perform a reservation communication.

First, equipment connected with the transmitting-end communicationapparatus #1 issues a reservation instruction 51 and thetransmitting-end communication apparatus #1 issues a reservation request52 to the receiving-end communication apparatus #2. At this point,parameters of an approximate amount of requested reservationcommunication are exchanged.

In response to the reservation request, the communication apparatus #2that serves as a receiving-end of reservation communication uses anacknowledgement notification and a beacon 54 to notify of a slotavailable for communication and so on.

Further, the transmitting-end communication apparatus #1 determines aslot to be utilized for a reservation communication, based on theacknowledgement notification 53 and the beacon 54, and uses a beacon 55to notify the neighbors about the slot to be utilized.

Thereafter, when the slot to be utilized arrives, the transmitting-endcommunication apparatus #1 actually performs reservation communication56 to the receiving-end communication apparatus #2.

Thereafter, as long as a series of reservation communications iscontinued, a beacon 57 of the receiving-end communication apparatus #2continuously notifies of slot information utilized. Further, after theend of the communication, when time that has been indicated by the slotinformation utilized is left, other communication apparatuses #0 and #3can utilize the slot and can perform, for example, random access basedon the CSMA/CA.

Similarly, thereafter, as long as a series of reservation communicationsis continued, a beacon 58 of the transmitting-end communicationapparatus #1 continuously notifies of slot information utilized and areservation communication 59 is performed. After the end of thecommunication, when time indicated by the slot information utilized isleft, other communication apparatuses #0 and #3 can utilize the slot andcan perform, for example, random access based on the CSMA/CA.

The communication apparatus #1 and the communication apparatus #2 issuerespective beacons in which slot information is described to neighboringcommunication apparatuses. In this case, the beacon from thecommunication apparatus #1 reaches the communication apparatus #0, whichis a hidden terminal from the communication terminal #2, and the beaconfrom the communication apparatus #2 reaches the communication apparatus#3, which is a hidden terminal from the communication apparatus #1. Thatis, a notification indicating that a reservation communication is to beperformed is issued within the both communication ranges of thetransmitting-end communication apparatus #1 and the receiving-endcommunication apparatus #2. Other communication apparatuses #0 and #3that have received the notification are adapted not to perform intendedcommunication operations using the reserved slot. As a result, collisionand interference are avoided and a bandwidth is guaranteed.

The transmitting-end communication apparatus #1 and the receiving-endcommunication apparatus #2 can use a slot for which reservationintension is indicated, with priority. Another communication apparatuscannot unconditionally use the slot for which the reservation intensionis indicated, unless it undergoes a special and additional procedure(which is not explained in the description), such as clearing thereservation intension.

In the example shown in FIG. 5, although the reservation processingsequence is performed in response to a request from a transmitting side,the reservation processing sequence can also be performed in response toa request from a receiving side. For example, an example of such a caseis that a receiving-end communication apparatus issues acontent-distribution request to a transmitting-end communicationapparatus. FIG. 6 shows a sequence of reservation processing performedby a receiving side. In the illustrated example, equipment connectedwith the communication apparatus #2 that serves as a receiving-end ofreservation communication issues a reservation instruction and thetransmitting-end communication apparatus #1 responds thereto to therebyperform a reservation communication.

First, equipment connected with the receiving-end communicationapparatus #2 issues a reservation instruction 61 and the receiving-endcommunication apparatus #2 issues a reservation notification 62 to thetransmitting-end communication apparatus #1. At this point, parametersof an approximate amount of requested reservation communication areexchanged.

In this case, in conjunction with the reservation notification, a beaconnotification 63 may notify the neighboring communication apparatusesthat a reservation communication is to be performed.

The transmitting-end communication apparatus #1 that has received thereservation notification determines a slot to be utilized for thereservation communication and uses a beacon 64 to notify the neighborsabout the slot to be utilized.

Thereafter, when the slot to be utilized arrives, the transmitting-endcommunication apparatus #1 actually performs a reservation communication65 to the receiving-end communication apparatus #2.

Thereafter, as long as a series of reservation communications iscontinued, a beacon 66 of the receiving-end communication apparatus #2continuously notifies of slot information utilized. After the end of thecommunication, when time indicated by the slot information utilized isleft, other communication apparatuses #0 and #3 can utilize the slot andcan perform, for example, random access based on the CSMA/CA.

Similarly, thereafter, as long as a series of reservation communicationsis continued, a beacon 67 of the transmitting-end communicationapparatus #1 continuously notifies of slot information utilized and areservation communication 68 is performed. After the end of thecommunication, when time indicated by the slot information utilized isleft, other communication apparatuses #0 and #3 can utilize the slot andcan perform, for example, random access based on the CSMA/CA.

The communication apparatus #1 and the communication apparatus #2 issuerespective beacons in which slot information is described to neighboringcommunication apparatuses. In this case, the beacon from thecommunication apparatus #1 reaches the communication apparatus #0, whichis a hidden terminal from the communication terminal #2, and the beaconfrom the communication apparatus #2 reaches the communication apparatus#3, which is a hidden terminal from the communication apparatus #1. Thatis, a notification indicating that a reservation communication is to beperformed is issued to within the both communication ranges of thetransmitting-end communication apparatus #1 and the receiving-endcommunication apparatus #2. Other communication apparatuses #0 and #3that have received the notification are adapted not to perform intendedcommunication operations using the reserved slot. As a result, collisionand interference are avoided and a bandwidth is guaranteed.

The transmitting-end communication apparatus #1 and the receiving-endcommunication apparatus #2 can use a slot for which reservationintension is indicated, with priority. Another communication apparatuscannot unconditionally use the slot for which the reservation intensionis indicated, unless it undergoes a special and additional procedure(which is not described in the specification), such as clearing thereservation intension.

The configuration of superframe of each wireless communication apparatusin the ad-hoc network according to this embodiment has already beendescribed with reference to FIG. 3. FIG. 7 shows an example of theconfiguration of a superframe for performing a reservation communicationin the ad-hoc network.

In the communication apparatus #1, a period from a beacon (B1) to a nextbeacon (B1′) (not shown) is defined as a superframe period (SF1). Withregard to the communication apparatus #2, when it transmits a beacon(B2), a superframe period (SF2) is defined and a period prior thereto istreated as a superframe period (SF2-1) (not shown). Further, with regardto the communication apparatus #3, when it transmits a beacon (B3), asuperframe period (SF3) is defined and a period prior thereto is treatedas a superframe period (SF3-1).

In this case, the communication apparatus #1 receives a beacon (N2) fromthe communication apparatus #2 located in the vicinity. Thecommunication apparatus #2 receives a beacon (N1) from the communicationapparatus #1 in the vicinity and a beacon (N3) from the communicationapparatus #3. The communication apparatus #3 also receives the beacon(N2) from the communication apparatus #2 in the vicinity.

In this embodiment, when each communication apparatus autonomouslydetermines a superframe period, the communication apparatus periodicallynotifies of a portion for a reservation communication by using a beaconsignal, so that the neighboring communication apparatuses are notifiedof the presence of the reservation communication. In the example shownin FIG. 7, the communication apparatus #1 that serves as a transmittingend of reservation communication performs a reservation communication(RTX) 71 to the receiving-end communication apparatus #2. Insynchronization with the timing, the receiving-end communicationapparatus #2 performs a reception (RRX) 72.

Through the use of the beacon (B1) from the transmitting-endcommunication apparatus #1 and the beacon (B2) from the receiving-endcommunication apparatus #2, the neighbors are notified of an intensionindication for a reservation communication. Accordingly, thecommunication apparatus #3, which is a hidden terminal from thecommunication apparatus #1, can detect the utilization of a slot for areservation communication in advance. Thus, in the time period 73, thecommunication apparatus does not perform a communication operationunconditionally, so that collision and interference are avoided and abandwidth is guaranteed.

A superframe period is constituted by a plurality of slots and a slot isa minimum unit of access. FIG. 8 shows an example of arrangement ofslots recognized by each communication apparatus itself when performinga reservation communication. With reference to its own superframeperiod, the wireless communication apparatus arranges the slots in termsof a relative position at which a beacon signal is received from aneighboring communication apparatus (as described above).

It is shown that the communication apparatus #1 receives a beacon fromthe communication apparatus #2, at the 32nd position, with the ownbeacon transmission position being 0th position. It is shown that, withthe own beacon transmission position being 0th position, thecommunication apparatus #2 receives a beacon from the communicationapparatus #3, at the 18th position, and receives a beacon from thecommunication apparatus #1, at the 32nd position. It is shown that thecommunication apparatus #3 receives a beacon from the communicationapparatus #2, at the 48th position, with the own beacon transmissionposition being 0th position.

Further, each communication apparatus notifies of a slot portion usedfor a reservation communication as in the case in which a beacon isreceived from another communication apparatus, thereby informing that areservation communication is to be performed.

That is, it is shown that the transmitting-end communication apparatus#1 utilizes the 4th slot to the 13th slot for a reservationcommunication in terms of a relative position from its own beacontransmission position.

Similarly, it is shown that the receiving-end communication apparatus #2utilizes the 36th slot to the 45th slot for a reservation communicationin terms of a relative position from its own beacon transmissionposition.

In the illustrated example, for the sake of convenience, thetransmitting-side and receiving-side communication apparatuses treat areservation period as in the case of receiving a beacon signal fromanother communication apparatus and notify of the reservation period asin the case of receiving a beacon signal. With this arrangement, even awireless communication apparatus that exists in a region to be a hiddenterminal viewed from a transmitting-side communication apparatus can benotified that a bandwidth-guaranteed communication is being performed.Through the use of utilization-recognition slot information (describedbelow) described in existing beacon information, it is possible tonotify of a slot utilized for a reservation communication.

The communication apparatus #3 that is located at a position so as to bea hidden terminal from the transmitting-end communication apparatus #1analyzes utilization slot information described in a beacon transmittedfrom the receiving-end communication apparatus #2. By doing so, thecommunication apparatus #3 can recognize that there is a possibilitythat the 20th slot to the 29th slot, in terms of a relative positionfrom its own beacon transmission position, are used for communication ofneighboring communication apparatuses.

When neighboring communication apparatuses are notified of such a slotarrangement relationship as a parameter of utilization slot informationthrough the use of a periodically transmitted beacon, it is possible tonotify that a reservation communication is to be performed in an ad-hocnetwork.

When neighboring communication apparatuses are notified of such a slotarrangement relationship as a parameter of utilization slot informationthrough the use of a periodically transmitted beacon, it is possible tonotify that a reservation communication is to be performed in an ad-hocnetwork.

In this embodiment, an RTS/CTS system is employed as means for improvingthe quality of communication in a communication environment in whichrandom access is performed based on the CSMA/CA in the ad-hoc network inwhich no controlling station is provided. That is, in this case, priorto transmission of substantial information, a transmitting-endcommunication apparatus transmits an RTS (Request to Send: atransmission request) and a receiving-end communication apparatusreceives the RTS. When data is receivable, the receiving-endcommunication apparatus returns a CTS (Clear to Send: a receptionpreparation completion) as a response to the RTS. After a connection isestablished through the RTS/CTS information exchange between theapparatuses, data transmission is executed.

FIG. 9 shows an example of a sequence of communication in a reservationperiod. The example shown in this figure illustrates a sequence for acase in which the transmitting-end communication apparatus #1 performs areservation communication to the receiving-end communication apparatus#2. In a reservation period, however, data transmission is executedafter the exchange of RTS/CTS information.

When a reservation period arrives, the transmitting-end communicationapparatus #1 confirms that another wireless communication apparatus isnot communicating. Thereafter, the transmitting-end communicationapparatus #1 transmits a predetermined preamble signal (P) 91 and thentransmits a pseudo beacon (PSB) 92 and a transmission request (RTS) 93.The pseudo beacon is transmitted in order to cause the transmitting-sideand receiving-side communication apparatuses to treat a reservationperiod as in the case of receiving a beacon signal from anothercommunication apparatus and to notify of the reservation period as inthe case of receiving a beacon signal.

While not shown here, when other wireless communication apparatusescommunicate with each other, the communication apparatus #1 performscontrol for restraining the transmission of a signal until thecommunication is completed.

In the RTS, the communication apparatus #2 that is a receiving end ofinformation when a reservation communication is performed is specified(described below). Upon receiving the RTS, the receiving-endcommunication apparatus #2 recognizes that communication is to beperformed later and returns a predetermined preamble (P) 94 and then areception preparation completion (CTS) 95.

While not shown here, when other wireless communication apparatusescommunicate with each other, the communication apparatus #2 may performcontrol for, for example, restraining the transmission of a signal untilthe communication is completed.

In response to the CTS signal, the transmitting-end communicationapparatus #1 starts transmission of a predetermined preamble signal (P)96 and then transmission of data (data) 97 to theinformation-receiving-end communication apparatus #2.

Further, the receiving-end communication apparatus #2 receives the data.When the data reception is finished, the receiving-end communicationapparatus #2 also returns a predetermined preamble signal (P) 98 andthen returns a reception acknowledgement (ACK) 99 as required.

Based on the reception acknowledgement (ACK) 99 transmitted from thereceiving-end communication apparatus #2, the transmitting-endcommunication apparatus #1 can recognize that the series of informationtransmissions has been completed.

FIG. 10 shows an example of the frame structure of a beacon signal. Inthis embodiment, each communication apparatus that operates in thead-hoc network transmits a beacon signal in the beginning of its ownsuperframe period.

The illustrated beacon frame includes a type indicating that transmittedinformation is beacon information, a length indicating the informationlength of the frame, a MAC address that serves as the addressinformation of a transmitting-end, a timing indicating timinginformation of transmission, a network ID indicating a group to which acorresponding communication apparatus belongs, an error detection codeCRC (which is attached as required) up to this portion,utilization-recognition slot information that notifies of parameterssuch as a reservation communication according to the present invention,and an error detection code CRC of the entire frame.

As described above, in the utilization-recognition slot information, areservation period is treated as in the case of receiving a beaconsignal from another communication apparatus and is described as in thecase of receiving a beacon signal. A communication apparatus that hasreceived and analyzed a beacon signal can detect a slot to be utilizedfor a reservation communication. The communication apparatus thenrestrains communication using the reserved slot, so that collision andinterference are avoided and a bandwidth is guaranteed during thereservation communication.

FIG. 11 shows an example of the frame structure of reservation requestcommand information. When equipment connected with areservation-communication-transmitting-end communication apparatusissues a reservation instruction, a reservation request command istransmitted to a receiving-side communication apparatus (see FIG. 5).

The illustrated command frame includes a type indicating thattransmitted information is a reservation request command, a lengthindicating the information length of the frame, a receiving-end MACaddress that serves as the address information of a receiving end, atransmitting-end MAC address that serves as the address information of atransmitting end, a command that describes parameters specific to thecommand, an error detection code CRC that is attached as required andthat indicates an error up to this point, request slot information thatconveys a request for a reservation communication according to thepresent invention, and an error detection code CRC of the entire frame.

FIG. 12 shows an example of the frame structure ofacknowledgement-notification command information. Anacknowledgement-notification command is transmitted by a receiving-endcommunication apparatus in response to a reservation request from acommunication apparatus that serves as a transmitting end of reservationcommunication (see FIG. 5).

The illustrated command frame includes a type indicating thattransmitted information is an acknowledgement-notification command, alength indicating the information length of the frame, a receiving-endMAC address that serves as the address information of a receiving end, atransmitting-end MAC address that serves as the address information of atransmitting end, a command that describes parameters specific to thecommand, an error detection code CRC that is attached as required andthat indicates an error up to this point, utilization slot informationthat indicates a position utilized for a reservation communicationaccording to the present invention, and an error detection code CRC ofthe entire frame.

In the utilization slot information, a reservation period is treated asin the case of receiving a beacon signal from another communicationapparatus and is described as in the case of receiving a beacon signal(as described above).

FIG. 13 shows an example of the frame structure of reservationnotification command information. A reservation notification command istransmitted from a receiving-end communication apparatus to atransmitting-end communication apparatus when the receiving end issues arequest for a reservation communication (see FIG. 6).

FIG. 13 shows an example of the frame structure of reservationnotification command information. A reservation notification command istransmitted from a receiving-end communication apparatus to atransmitting-end communication apparatus when the receiving end issues arequest for a reservation communication (see FIG. 6).

In the utilization slot information, a reservation period is treated asin the case of receiving a beacon signal from another communicationapparatus and is described as in the case of receiving a beacon signal(as described above).

FIG. 14 shows an example of the frame structure of the pseudo beacon.The pseudo beacon signal is transmitted from a transmitting-endcommunication apparatus when a reservation period arrives. The pseudobeacon is transmitted in order to cause the transmitting-side andreceiving-side communication apparatuses to treat a reservation periodas in the case of receiving a beacon signal from another communicationapparatus and to notify of the reservation period as in the case ofreceiving a beacon signal.

The illustrated pseudo-beacon frame includes a type indicating thattransmitted information is a pseudo beacon, a length indicating theinformation length of the frame, a MAC address that serves as theaddress information of a transmitting end, a timing indicating timinginformation of transmission, a network ID indicating a group to which acorresponding communication apparatus belongs, and an error detectioncode CRC of the entire frame.

FIG. 15 shows an example of the frame structure of the RTS command.

The illustrated RTS command frame includes a type indicating thattransmitted information is an RTS command, a length indicating theinformation length of the frame, a receiving-end MAC address that servesas the address information of a receiving end, a transmitting-end MACaddress that serves as the address information of a transmitting end, anRTS parameter that describes a parameter specific to the command, and anerror detection code CRC of the entire frame.

FIG. 16 shows an example of the frame structure of the CTS command.

The illustrated CTS command frame includes a type indicating thattransmitted information is a CTS command, a length indicating theinformation length of the frame, a receiving-end MAC address that servesas the address information of a receiving end, a transmitting-end MACaddress that serves as the address information of a transmitting end, aCTS parameter that describes a parameter specific to the command, and anerror detection code CRC of the entire frame.

FIG. 17 shows an example of the frame structure of a data frame.

The illustrated data frame includes a type indicating that transmittedinformation is data, a length indicating the information length of theframe, a receiving-end MAC address that serves as the addressinformation of a receiving end, a transmitting-end MAC address thatserves as the address information of a transmitting end, an attributethat describes the attribute of the data, an error detection code CRCthat is attached as required and that indicates an error up to thispoint, data payload information containing actual data, and an errordetection code CRC of the entire frame.

FIG. 18 shows an example of the frame structure of the ACK frame.

FIG. 18 shows an example of the frame structure of the ACK frame.

FIG. 19 shows operational procedures of a wireless communicationapparatus in the ad-hoc network according to the present invention in aflow chart form.

First, a determination is made as to whether or not a reservationinstruction from equipment connected with a wireless communicationapparatus via the interface is received (step S1). When a reservationinstruction is accepted, the amount of communication required for thereservation communication is calculated (step S2). At this point, adetermination is made as to whether or not the self is a transmittingend (step S3). When the self is a transmitting end, a reservationrequest command is transmitted to a receiving end (step S4). On theother hand, when the self is not a transmitting end, a slot to beutilized is determined (step S5) and a reservation notification commandis transmitted to the transmitting end (step S6). Subsequently, anotification indicating the utilization of communication is issued usinga beacon (step S7).

When a reservation instruction is not received in step S1, adetermination is made as to whether or not a reservation request commandis wirelessly received (step S8). When a reservation request command isreceived, request slot information described in the command is obtained(step S9). After the request slot information is converted into slotinformation of the self (step S10), a slot to be actually utilized forcommunication is determined (step S11) and anacknowledgement-notification command is returned to the transmitting-endcommunication apparatus (step S12). Subsequently, a notificationindicating the utilization of communication is issued using a beacon(step S7).

When a reservation request command has not been received in step S8, adetermination is made as to whether or not a reservation notificationcommand is received (step S13) or a determination is made as to whetheror not an acknowledgement-notification command is received (step S14).When the notification command(s) is received, utilization slotinformation described in the command is obtained (step S15). Theutilization slot information is converted into slot information of theself (step S16) and then communication timing is set (step S17).Subsequently, a notification indicating the utilization of communicationis issued using a beacon (step S7).

On the other hand, when neither of the reservation notification commandnor the acknowledgement-notification command is received, adetermination is further made as to whether reservation communicationtiming has arrived (step S18). Then, in a case in which the reservationcommunication timing has arrived, when the self is a transmitting end(step S19), information for the reservation communication is transmitted(step S20). When the self is not a transmitting end, information for thereservation communication is received (step S21).

When the reservation communication timing has not arrived in step S18, adetermination is made as to whether or not a beacon signal from anothercommunication apparatus is received (step S22). When a beacon signal isreceived, utilization slot information described therein is obtained(step S23), and a portion (slot) of the information which can beutilized by the self for communication is stored in the informationstorage 102 (step S24).

Second Embodiment

In the first embodiment described above according to the presentinvention, each of a transmitting-end communication apparatus and areceiving-end communication apparatus sets a reservation period in itsown superframe and uses a beacon signal to notify the neighboringcommunication apparatuses about the position information of slotsassociated with the reservation period. Each communication apparatusrestrains a communication operation in the reservation period set byanother communication apparatus, thereby preventing communicationcollision and interference. Thus, this arrangement can achieveisochronous communication based on band reservation in an ad-hoc networkand can guarantee a bandwidth during the transmission of isochronousdata such as AV content.

However, a reservation period is an exclusive time period and thus atransmission path is exclusively occupied by specific communicationapparatuses. In a method for performing communication by exclusivelyoccupying a transmission path over a predetermined communication band(time), when isochronous communication that does not fill apredetermined communication band (time) that has been once set isperformed, the insufficient portion cannot be used for communicationbetween other communication apparatuses and thus the throughputdecreases.

On the other hand, in an access control method based on the CSMA/CA,communication is started when a carrier signal is not detected. Thus,there is no guarantee that transmission path is exclusively occupied andutilized for a specific communication.

Accordingly, in a second embodiment of the present invention, a wirelesscommunication apparatus, which is included in a ad-hoc network in whichindividual communication stations forms a network in an autonomousdistributed manner without the relationship of a controlling station anda controlled station, sets a period (timing) usable by the self withpriority and performs isochronous communication in the priorityutilization period as required.

The priority utilization period is a period that a communicationapparatus can utilize with priority and is different from a reservationperiod in which a communication apparatus that has made a reservationexclusively uses a transmission path. Thus, while a communicationapparatus sets a period utilizable with priority to perform anisochronous communication, arbitrary communication between othercommunication apparatuses is permitted when that isochronouscommunication has not been performed or the isochronous communicationhas been finished.

Even in a case in which the self has set a period utilizable withpriority, when another communication is performed, the start of anisochronous communication is temporarily delayed and transmission isperformed after the communication is finished. In this case, it ispossible to achieve an isochronous communication that coexists withanother communication. Also, while the start of a priority utilizationperiod is temporarily delayed, it can be expected that the throughput isimproved in terms of the entire system and the temporary delay isrecovered. This is because the priority utilization state, i.e., thepriority utilization of a band, is automatically released when anisochronous communication that does not fill the priority utilizationperiod is performed.

FIG. 20 shows a state in which each communication apparatus arrangespriority utilization periods in its own superframe in the ad-hoc networkaccording to this embodiment.

The communication apparatus #1 that serves as a transmitting endarranges priority utilization periods S1 to S5 in a superframe periodSF1 defined by beacon signals B1 and B1′, in accordance with isochronousinformation I1 to I5 transmitted from an application #1 of equipmentconnected via the interface 101.

In the example shown in the figure, priority utilization periods are setat a period that is synchronized with the isochronous information thatarrives almost periodically. However, since the priority utilizationperiods S1 to S5 for transmission are set so as to avoid timing at whicha beacon signal from another communication apparatus is received, thepriority utilization periods are not necessarily arranged at regularintervals.

On the other hand, the communication apparatus #2 that serves as areceiving end of isochronous communication receives data transmitted attimings R1 to R5 that are synchronized with the priority utilizationperiods of the transmitting-end communication apparatus #1. Thecommunication apparatus #2 delivers the data, as isochronous informationI1′ to I5′, to an application #2 of the equipment connected via theinterface 101, while considering a predetermined amount of transmissiondelay.

In this case, similarly to the transmitting-end communication apparatus#1, the communication apparatus #2 may set, as priority utilizationperiods for reception, R1 to R5 in a superframe period SF2 defined by abeacon signal B2.

Priority utilization periods are continuously set for each superframeperiod until an isochronous communication is finished. When a newwireless communication apparatus appears in the vicinity, the priorityutilization periods may be rearranged, for example, by shifting so as toavoid beacon transmission timing of the communication apparatus.

In the example shown in FIG. 20, although the priority utilizationperiods are arranged for each piece of isochronous information, aplurality of pieces of isochronous information may be gathered so as toarrange one priority utilization period. FIG. 21 shows a state in whicha plurality of pieces of isochronous information are gathered to arrangea priority utilization period.

The transmitting-end communication apparatus #1 arranges priorityutilization periods S11 to S16 for transmission in a superframe periodSF1 defined by beacon signals B1 and B1′, in accordance with isochronousinformation I1 to I13 transmitted from an application #1 of equipmentconnected via the interface 101.

In the illustrated example, the priority utilization period S11 isarranged for a plurality of pieces of isochronous information I1 to I2,and thereafter, the priority utilization period S12 is sequentiallyarranged for the isochronous information I3 and I4.

As in the case shown in FIG. 20, priority utilization periods are set ata period that is synchronized with a plurality of pieces of isochronousinformation which arrive almost periodically. However, since thepriority utilization periods S11 to S16 for transmission are set so asto avoid timing at which a beacon signal from another communicationapparatus is received, the priority utilization periods are notnecessarily arranged at regular intervals.

On the other hand, the communication apparatus #2 that serves as areceiving end of isochronous communication receives data transmitted attimings R11 to R16 that are synchronized with the priority utilizationperiods of the transmitting-end communication apparatus #1. Thus, thecommunication apparatus #2 delivers the data, as a plurality of piecesof isochronous information I1′ to I12′, to an application #2 of theequipment connected via the interface 101, while considering apredetermined amount of transmission delay.

In this case, similarly to the transmitting-end communication apparatus#1, the communication apparatus #2 may set, as priority utilizationperiods for reception, R11 to R16 in a superframe period SF2 defined bya beacon signal B2.

Priority utilization periods are continuously set for each superframeperiod until an isochronous communication is finished. When a newwireless communication apparatus appears in the vicinity, the priorityutilization periods may be rearranged, for example, by shifting so as toavoid beacon transmission timing of the communication apparatus.

FIG. 22 shows an example of a sequence of communication in a priorityutilization period. The example shown in this figure illustrates asequence for a case in which the transmitting-end communicationapparatus #1 transmits/receives isochronous information to/from thereceiving-end communication apparatus #2 by utilizing a priorityutilization period. After the transmitting-end communication apparatus#1 and the receiving-end communication apparatus #2 finish the priorityutilization of the priority utilization period, the neighboringcommunication apparatuses #4 and #0 perform ordinary random access basedon a CSMA/CA system. Each communication apparatus executes datatransmission after exchanging RTS/CTS information, in order to improvethe quality of communication.

First, when another communication is not performed in the priorityutilization period, the communication apparatus #1 that serves as atransmitting end transmits a predetermined synchronization-signalpreamble (P) 501 and a transmission request (RTS) 502 to thecommunication apparatus #2 that serves as a receiving end. In this case,upon transmission of the RTS, priority utilization time is started inthe priority utilization period.

The communication apparatus #2 receives the RTS, and when the datacommunication is possible, the communication apparatus #2 returns apredetermined synchronization-signal preamble (P) 503 and a receptionpreparation completion (CTS) 504 to the communication apparatus #1.

The communication apparatus #2 receives the RTS, and when the datacommunication is possible, the communication apparatus #2 returns apredetermined synchronization-signal preamble (P) 503 and a receptionpreparation completion (CTS) 504 to the communication apparatus #1.

Further, when the data was successively received, the communicationapparatus #2 returns a reception acknowledgement (ACK) 509 together witha predetermined synchronization-signal preamble (P) 508. In this case,although an example of a sequence configuration for receiving the ACKimmediately after the data transmission is illustrated for the sake ofconvenience, the reception acknowledgement ACK may be returned whennecessary.

Subsequently, when there is communication with another communicationapparatus, the communication apparatus #1 that has set the priorityutilization time can transmit/receive data by transmitting a preamble510 and a transmission request (RTS) 511 again, as required.

At this point, when the communication apparatus #1 does not performcommunication, the setting of the priority utilization time is cleared,so that other communication apparatuses #4 and #0 can communicate witheach other without undergoing any special procedure.

That is, even in the priority utilization period, when the communicationapparatus #4 does not receive the preamble (P) 510, the headerinformation (H) 511, and so on from the communication apparatus #1, thecommunication apparatus #4 determines that the priority utilization timehas finished. Then, in order communicate to the communication apparatus#0, the communication apparatus #4 transmits a predeterminedsynchronization-signal preamble (P) 512 and a transmission request (RTS)513 to the communication apparatus #0.

The communication apparatus #0 receives the RTS, and when the datacommunication is possible, the communication apparatus #0 returns apredetermined synchronization-signal preamble (P) 514 and a receptionpreparation completion (CTS) 515 to the communication apparatus #4.

Upon receiving the CTS, the transmitting-end communication apparatus #4transmits a predetermined synchronization-signal preamble (P) 516,header information (H) 517, and a data payload (Data) 518 to thecommunication apparatus #0.

The priority utilization period is a period that a communicationapparatus can utilize with priority and is different from a reservationperiod in which a communication apparatus that has made a reservationexclusively uses a transmission path. Thus, while a communicationapparatus sets a period utilizable with priority to perform anisochronous communication, ordinary random access is permitted based ona CSMA/CA system when that isochronous communication is not performed orthe prioritized isochronous communication has been finished in thepriority utilization period. Accordingly, even when isochronouscommunication that does not fill a priority utilization period that hasbeen once set is performed, the insufficient portion can instead be usedfor communication between other communication apparatuses, thusimproving the throughput.

FIG. 23 shows another example of a sequence of communication in apriority utilization period. The example shown in this figureillustrates a sequence for a case in which the transmitting-endcommunication apparatus #1 transmits/receives isochronous informationto/from the receiving-end communication apparatus #2 by utilizing apriority utilization period. In a case in which another communication isstill being performed at a point of time when a priority utilizationperiod set by the self arrives, the start of an isochronouscommunication is temporarily delayed and transmission is performed afterthe communication finishes.

First, when a communication (previous data) 601 from anothercommunication apparatus #0 is performed in a priority utilizationperiod, the communication apparatus #1 that serves as a transmitting endsets the period as transmission disabled time until that communicationfinishes. Alternatively, the communication apparatus #1 may perform areception operation in advance prior to the priority utilization periodso as to be able to recognize the communication duration time of theprevious data 601 in advance.

Then, when the transmission disabled time ends, the communicationapparatus #1 transmits a predetermined synchronization-signal preamble(P) 602 and a transmission request (RTS) 603 to the communicationapparatus #2 that serves as a receiving end. In this case, upon thetransmission of the RTS, the priority utilization time in the priorityutilization period is started.

The communication apparatus #2 receives the RTS, and when the datacommunication is possible, the communication apparatus #2 returns apredetermined synchronization-signal preamble (P) 604 and a receptionpreparation completion (CTS) 605 to the communication apparatus #1.

In response to the CTS, the transmitting-end communication apparatus #1transmits a predetermined synchronization-signal preamble (P) 606,header information (H) 607, and a data payload (Data) 608 to thecommunication apparatus #2.

Further, when the data was successively received, the communicationapparatus #2 returns a predetermined synchronization-signal preamble (P)609 and a reception acknowledgement (ACK) 610 to the communicationapparatus #1. In this case, although an example of a sequenceconfiguration for receiving the ACK immediately after the datatransmission is illustrated for the sake of convenience, the receptionacknowledgement ACK may be returned when necessary.

In a case in which another communication is being performed at a pointof time when a priority utilization period set by the self arrives, thestart of an isochronous communication is temporarily delayed, and atransmission based on the priority utilization is performed after thatcommunication finishes. This can realize an isochronous communicationthat coexists with another communication. In this case, the start of thepriority utilization period is temporarily delayed. When isochronouscommunication that does not fill the priority utilization period isperformed, it can be expected that the throughput is improved in termsof the entire system and the temporary delay is recovered, since thepriority utilization state, i.e., a band, is released (see FIG. 22).

For convenience, FIGS. 22 and 23 show an example of procedures forstarting data communication after the transmission request RTS and thereception preparation completion CTS are exchanged. Alternatively, thecommunication sequence may be configured so as to directly start datacommunication without going through the RTS/CTS exchange procedures.

FIG. 24 shows a communication sequence for exchanging a priorityutilization period between communication apparatuses that performisochronous communication.

In the illustrated example, the application #1 that performs anisochronous communication notifies the central controller 103 via theinterface 101 of the transmitting-end wireless communication apparatus#1 about parameter information, as an isochronous communicationinstruction 81, for the isochronous communication.

In response to the isochronous communication notification, the wirelesscommunication apparatus #1 transmits a priority-utilization-periodnotification command 82 to the receiving-end wireless communicationapparatus #2.

Subsequently, in response to the priority-utilization-periodnotification command 82, the receiving-end wireless communicationapparatus #2 stores priority-utilization-period information utilizableby the self in the information storage 113. The wireless communicationapparatus #2 also describes the priority-utilization-period informationin a beacon notification 83 and transmits the beacon notification 83 towireless communication apparatuses that exist in the neighbor.

Upon receiving the beacon notification 83, the wireless communicationapparatus #1 issues a notification 84 indicating that an isochronouscommunication has become possible to the application #1. Further, thewireless communication apparatus #1 stores thepriority-utilization-period information used for the isochronouscommunication in the information storage 113. The wireless communicationapparatus #1 also describes the priority-utilization-period informationin a beacon notification 85 and transmits the beacon notification 85 towireless communication apparatuses that exist in the neighbor.

The wireless communication apparatus #2 receives the beacon notification85, and issues a notification 86 indicating the start of the isochronouscommunication to an application #2 that serves as a receiving end. Atthis point, the setting of the priority utilization period in asuperframe is completed.

Subsequently, an isochronous communication using the priorityutilization period is started. That is, the application #1 continuouslystarts an isochronous communication 87 to the wireless communicationapparatus #1. Further, the wireless communication apparatus #1continuously performs a priority-utilization-period communication 88,within the previously-set priority utilization period, to the wirelesscommunication apparatus #2.

The wireless communication apparatus #2 then continuously performs anisochronous communication 89 to the application #2.

FIG. 25 shows another example of a communication sequence for exchanginga priority utilization period between communication apparatuses thatperform isochronous communication. In this case, the receiving-endcommunication apparatus is adapted to exchangepriority-utilization-period information by using apriority-utilization-period notification command instead of a beacon.

In the illustrated example, the application #1 that performs anisochronous communication notifies the central controller 103 via theinterface 101 of the transmitting-end wireless communication apparatus#1 about parameter information, as an isochronous communicationinstruction 181, for the isochronous communication.

In response to the notification, the wireless communication apparatus #1transmits a priority-utilization-period notification command 182 to thewireless communication apparatus #2 that serves as a receiving end.

In response to the priority-utilization-period notification command 182,the receiving-end wireless communication apparatus #2 storespriority-utilization-period information utilizable by the self in theinformation storage 113. The wireless communication apparatus #2 alsotransmits the priority-utilization-period information to thetransmitting-end wireless communication apparatus #1 as apriority-utilization-period notification command 183. The wirelesscommunication apparatus #2 then issues a notification 184 indicating thestart of isochronous communication to an application #2 that serves as areceiving end.

In response to the priority-utilization-period notification command 183from the wireless communication apparatus that serves as the receivingend, the wireless communication apparatus #1 issues a notification 185indicating that an isochronous communication has become possible to theapplication #1 and also stores the priority utilization period used forthe isochronous communication in the information storage 113.

Then, the application #1 continuously starts an isochronouscommunication 186 to the wireless communication apparatus #1. Further,the wireless communication apparatus #1 continuously performs apriority-utilization-period communication 187, within the previously-setpriority utilization period, to the wireless communication apparatus #2.

The wireless communication apparatus #2 then continuously performs anisochronous communication 188 to the application #2.

FIG. 26 shows an example of the frame structure of beacon information.

The illustrated beacon frame includes a type indicating that transmittedinformation is beacon information, a length indicating the informationlength of the frame, a MAC address that serves as the addressinformation of a transmitting-end, a timing indicating timinginformation of transmission, a network ID indicating a group to which acorresponding communication apparatus belongs, an error detection codeCRC that is attached as required and that indicates an error up to thisportion, priority-utilization-period information that notifies ofparameters such as a priority-utilization-period communication accordingto the present invention, and an error detection code CRC of the entireframe.

FIG. 27 shows an example of the frame structure of thepriority-utilization-period notification command.

The illustrated command frame includes a type indicating thattransmitted information is a priority-utilization-period notificationcommand, a length indicating the information length of the frame, areceiving-end MAC address that serves as the address information of areceiving end, a transmitting-end MAC address that serves as the addressinformation of a transmitting end, a command that describes a parameterspecific to the command, an error detection code CRC that is attached asrequired and that indicates an error up to this point,priority-utilization-period information that conveys a request for apriority-utilization-period communication according to the presentinvention, and an error detection code CRC of the entire frame.

Since the frame structures of the RTS command, the CTS command, the dataframe, and the ACK are analogous to those shown in FIGS. 15 to 18,respectively, the descriptions thereof are omitted here.

FIG. 28 shows, in a flow chart form, processing procedures for awireless communication apparatus to set and clear a priority utilizationperiod in the ad-hoc network according to this embodiment.

When an isochronous communication instruction is accepted from anapplication (not shown) of equipment connected with the communicationapparatus via the interface 101 (step S31), the central controller 103analyzes a parameter described in the isochronous communicationinstruction, and obtains beacon-reception-time information from acommunication apparatus that is located in the vicinity, based onneighboring-communication-apparatus information stored in theinformation storage 113 (step S32).

While the parameter described in the isochronous communicationinstruction is analyzed, a priority utilization period is set so thatthe priority utilization period does not overlap the reception time(step S33). A priority-utilization-period notification command istransmitted to a communication apparatus that serves as a receiving end(step S34), and the series of processing exits.

On the other hand, when the received command is apriority-utilization-period notification command (step S35), thecontrol-signal analyzer 109 analyzes the command and obtainspriority-utilization-period information described in the command (stepS36). The control-signal analyzer 109 obtains beacon-reception-timeinformation from a communication apparatus located in the vicinity,based on neighboring-communication-apparatus information stored in theinformation storage 113 (step S37).

A priority utilization period is set so that the priority utilizationperiod does not overlap the beacon reception time (step S38). Further,the state of the setting is constructed as one piece of beaconinformation and is transmitted to neighboring communication apparatuses(step S39), and the series of processing exits.

When a beacon from the other end of communication is received (stepS40), the beacon analyzer 111 analyzes the beacon and obtainspriority-utilization-period information described therein (step S41).The communication start timing is set at the timing controller 105 (stepS42). Further, as required, a notification indicating the start ofcommunication is issued to the application of equipment connected (stepS43), and the series of processing exits.

Alternatively, when the result of analysis of the received beacon by thebeacon analyzer 111 indicates that the beacon has been transmitted fromanother new communication apparatus (step S44), thebeacon-reception-time information is stored in theneighboring-communication-apparatus information in the informationstorage 113 (step S45), and the series of processing exits.

When the central controller 103 determines that an isochronouscommunication has been discontinued over a predetermined period of time(step S46), the setting of the priority utilization period that has beenset is cleared (step S47). Further, the state of the setting isconstructed as one piece of beacon information, which is thentransmitted to the neighboring communication apparatuses (step S48). Theseries of processing then exits.

FIG. 29 shows, in a flow chart form, processing procedures for awireless communication apparatus to perform isochronous communication inthe ad-hoc network according to this embodiment.

When isochronous communication information is accepted from anapplication (not shown) of equipment connected with the communicationapparatus via the interface 101 (step S51), accepted data issequentially stored in the data buffer 102 (step S52), and the series ofprocessing exits.

Further, the central controller 103 checks whether or not the currenttime is within a priority utilization period (step S53). When thecurrent time is within a priority utilization period and the self is atransmitting-end communication apparatus (step S54), a determination ismade as to whether or not data stored in the data buffer 102 exists(step S55). When no data exists, the processing exits. When data exists,a determination is made as to whether or not another communicationapparatus is currently communicating (step S56). Unless anothercommunication apparatus is not communicating, processing fortransmitting a transmission request RTS is performed via thecontrol-signal generator 108 (step S57).

Thereafter, a determination is made as to whether or not thecontrol-information analyzer 109 has received a reception preparationcompletion CTS (step S58). When a reception preparation completion CTShas not been received, the processing exits. When a receptionpreparation completion CTS has been received, stored data is obtainedfrom the data buffer 102 (step S59). Predetermined header information isadded and then data transmission processing is performed (step S60).

Further, when a reception acknowledgement ACK is received (step S61),the series of processing exits. On the other hand, when an ACK has notbeen received, the process returns to step S56, and re-transmissionprocessing is performed after it is determined that communication ispossible on a transmission path.

When it is determined in step S54 that the self is not atransmitting-end communication apparatus, a determination is made as towhether or not the control-signal analyzer 109 has received atransmission request RTS (step S62). When an RTS is received, processingfor transmitting a reception preparation completion CTS is performed viathe control-signal generator 108 (step S63). Thereafter, processing forreceiving data is performed (step S64).

When the data was successively received (step S65), receptionacknowledgement information ACK is generated and is transmitted to thetransmitting end (step S66). The received data is decomposed intoisochronous information (step S67) and the isochronous information isstored in the data buffer 102 (step S68).

When isochronous communication time including a predetermined delay timearrives (step S69), the equipment connected via the interface 101 isinformed of the isochronous information, i.e., the data accumulated inthe data buffer 102 (step S70), and the series of processing exits.

When it is determined in step S53 that the current time is not within apriority utilization period, when it is determined in step S62 that atransmission request RTS is not received, and when it is determined thatthe data is not successively received in step S65, the process proceedsto step S69. In step S69, when isochronous communication time arrives,the equipment connected via the interface 101 is notified of theisochronous information (step S70), and the series of processing exits.

Supplement

The present invention has been described above in detail with referenceto the particular embodiments. However, it is obvious to those skilledin the art that a modification and substation can be made to theembodiments within the substance of the present invention. The presentinvention has been disclosed by way of example and should not beconstrued as limiting. The scope of the invention is to be determined bytaking the claims into consideration.

INDUSTRIAL APPLICABILITY

The present invention can provide a superior wireless communicationsystem, a wireless communication apparatus, a wireless communicationmethod, and a computer program which can perform data transmission witha guaranteed bandwidth in an ad-hoc communication environment.

The present invention can also provide a superior wireless communicationsystem, a wireless communication apparatus, a wireless communicationmethod, and a computer program which can efficiently transmit datahaving a real-time characteristic, such as AV content, throughisochronous communication in an ad-hoc communication environment.

According to the present invention, each wireless communication usesbeacon information to notify of timing that the self utilizes for aband-reservation communication. Thus, it is possible to achieveband-reservation communication without arranging a controlling station.

Further, a wireless communication apparatus that serves as a receivingend of information notifies of the neighbors about the presence of aband-reservation communication. By doing so, a wireless communicationapparatus that exists at a position to be a hidden terminal from atransmitting-end communication apparatus can be efficiently notified inadvance that a communication is performed.

Also, a beacon is used to inform of timing used for a band-reservationcommunication. By doing so, any large of number of wirelesscommunication apparatuses can be notified in advance that aband-reservation communication is performed.

Further, a receiving-end communication apparatus creates timing utilizedfor a band-reservation communication in a pseudo manner to have the samestate as timing of transmitting the own beacon and notifies of thetiming utilized for the band-reservation communication. By doing so, awireless communication apparatus that exists in a region to be a hiddenterminal viewed from a transmitting-end communication apparatus can alsobe notified that a band-reservation communication is performed.

Further, setting timing used for communication to have an interval atwhich a beacon period is divided by a predetermined timing can improvethe spatial repeated-use efficiency.

According to the present invention, each wireless communicationapparatus sets a period (timing) that can be utilized by the self withpriority so as to perform an isochronous communication. This can achieveisochronous communication without the provision of a controllingstation.

In this case, there is no need to occupy time that is periodicallydefined for a specific isochronous communication. When a predeterminedisochronous communication is finished, a period (timing) utilizable withpriority is temporarily released with priority, so as to appropriatelyallow other communication apparatuses to perform another communicationwith each other, thereby improving a throughput.

When communication between other wireless communication apparatuses isperformed in a period (timing) usable with priority, a predeterminedisochronous communication is started after the end of the communication.This can achieve an isochronous communication that coexists with anothercommunication. While a slight delay occurs in this case, it is possibleto achieve a real-time communication with an application of a receivingend.

According to the present invention, a period (timing) usable withpriority is set at timing that does not prevent the transmission of abeacon signal from another communication apparatus that exists in theown neighbor. This allows an isochronous communication while maintaininga coexistent relationship with neighboring communication apparatuses.

Further, each wireless communication apparatus mutually sets a period(timing) utilizable with priority. This can achieve communication withan enhanced real-time characteristic, without setting a period (timing)utilizable with priority which completely matches a cycle at which anapplication performs an isochronous communication.

1. (canceled)
 2. A first wireless communication device for exchangingbeacons with other wireless communication devices comprising: circuitryconfigured to transmit a request for reserving a radio resource for thefirst wireless communication device to a second wireless communicationdevice capable of wirelessly communicating with a third wirelesscommunication device, the third wireless communication device beinghidden from the first wireless communication device; receive a responseto the request from the second wireless communication device, theresponse specifying a period for transmitting data from the firstcommunication device; and transmit data at a timing based on the periodspecified in the response.